Hard formation was encountered in Yanyingzi geothermal well of Chengde where there were deviating force and complex lithology, the construction was difficult. Screw drill was adopted in accident treatment, deviation correction and compound drilling; the effects of screw drill application under these 3 working conditions are analyzed. Serious wear of conventional bit in hard rock drilling, low drilling speed and drilling collar fracture are solved by MD bit, and some improvement suggestions are put forward.